RAID array transformation in a pooled storage system

ABSTRACT

Aspects of the present invention relate to an apparatus and corresponding method that includes reading data from a first portion of an in-use redundant array of independent disks (RAID), wherein the first portion of the in-use RAID is arranged according to a first array configuration having at least a first parameter. One or more reserved extents in a storage pool is used to store at least a first portion of the data for writing to the in-use RAID. One or more free extents in the storage pool and/or in the in-use RAID is used to store at least a second portion of the data for writing to the in-use RAID. The data is written to a second portion of the in-use RAID. The second portion of the in-use RAID is arranged according to a second array configuration having at least a second parameter.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/223,160 filed Aug. 31, 2011, which claims priority from EuropeanPatent Application No. 10186887.5 filed Oct. 7, 2010, from each of whichpriority is claimed and which are herein incorporated by reference.

BACKGROUND

The present invention relates to the control of RAID storage, andparticularly to the transformation of RAID storage in a virtualizedstorage environment.

In a storage system where data is stored on one or more redundant-arraysof independent disks (RAID), parameters such as the number of disks inthe RAID, the size of the disks in the RAID and the RAID level used areusually fixed at array creation time. Once an array has been created anddata has been stored in it, it is usually not possible to change any ofthese parameters without deleting the array, destroying all the data,and re-creating the array with the new parameters.

Some conventional storage systems allow limited expansion of an array,e.g., from an array using RAID-5 with five disks to an array usingRAID-5 with 8 disks. However, this is currently accomplished by puttingnew capacity contiguously on the three new disks, and then recalculatingthe parity that already exists on the original five disks. Unfavorably,the new data is not striped across the array, and therefore the newdisks do not contribute to the parity overhead, which ultimately meansthe performance of systems created using this method is interior to thatof freshly created RAID-5 arrays with the same number of disks.Moreover, some conventional storage systems allow expansion from RAID-5to RAID-6 with the addition of a single disk, but even in cases allowingsuch an expansion, this is the only transformation allowed.

One conventional example of a facility for expanding an array by addingone or more new disks is disclosed in published PCT Patent Appl. No. WO2004/036424, which describes the transformation of an array to takeadvantage of the additional disk resource by a mechanism that scatters asubset of the existing data across the new disk space and subsequentlyinserts data in the remaining new disk space. Disadvantageously, oneconsequence of such conventional approaches is that the layout of thedata is substantially changed in the post-transformation array.

In other methods, it is possible to perform transformations of an in-usearray using RAID by reserving extents in each array upon creation of thearray, and furthermore ensuring that the reserved extents are isolatedfrom normal use, such that they can be brought into use during an arraytransformation. In this type of transformation, the system uses thereserved extents from the array to create a destination for data beingmoved as part of the transformation. Once the data is moved, theprevious storage location is free for use, and is utilized as thedestination for subsequent data to be moved, and so on, in the manner ofa “sliding window.” However, in this approach, there is the unfortunatepotential for mismatch between RAID stripes and underlying extents.Thus, when employing this methodology, the at least three extents shouldbe statically reserved on each array. The number of reserved extents mayalso be increased to allow the transformation system to increase thenumber of extent migrations in progress at any one time.

While the ability to perform array transformations in this way isadvantageous in systems of limited size, in large-scale systems, aconcomitant disadvantage exists. The primary drawback of requiringstatically reserved extents on each array from the time of its creationis that the number of reserved extents may only be chosen at arraycreation time, and cannot be specified or reserved at a later time.Moreover, once the reserve extents are created, it is difficult to altertheir structure or the number of reserved extents within the array. As aresult, in these conventional approaches, the effective capacity of thearrays is reduced, impacting system performance and frustrating one goalof RAID usage.

BRIEF SUMMARY OF INVENTION

A method according to one embodiment includes reading data from a firstportion of an in-use redundant array of independent disks (RAID),wherein the first portion of the in-use RAID is arranged according to afirst array configuration having at least a first parameter. One or morereserved extents in a storage pool is used to store at least a firstportion of the data for writing to the in-use RAID. One or more freeextents in the storage pool and/or in the in-use RAID is used to storeat least a second portion of the data for writing to the in-use RAID.The data is written to a second portion of the in-use RAID. The secondportion of the in-use RAID is arranged according to a second arrayconfiguration having at least a second parameter.

An apparatus according to one embodiment includes a control configuredto perform the foregoing method.

A computer program product according to one embodiment includes acomputer readable storage medium having computer readable program codeembodied therewith, the computer readable program code includingcomputer readable program code configured to perform the foregoingmethod.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a network architecture, in accordance with oneembodiment.

FIG. 2 shows a representative hardware environment that may beassociated with the servers and/or clients of FIG. 1, in accordance withone embodiment.

FIG. 3 shows an in-use RAID transformation system, according to oneembodiment.

FIG. 4 shows a flowchart of a method, according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified. It will be further understood thatthe terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

The following description discloses several preferred embodiments ofsystems, methods, and computer program products for transforming anin-use redundant array of independent disks (RAID) from a first arrayconfiguration having at least a first parameter to a second arrayconfiguration having at least a second parameter.

According to one general embodiment a system includes an extentreserving component adapted for reserving one or more extents in astorage pool, a data migrating component adapted for reading data from afirst portion of an in-use RAID, wherein the first portion of the in-useRAID is arranged according to a first array configuration having atleast a first parameter, using the one or more reserved extents in thestorage pool to store at least a first portion of the data for writingto the in-use RAID, using one or more free extents in the storage poolor in the in-use RAID to store at least a second portion of the data forwriting to the in-use RAID, and writing the data to a second portion ofthe in-use RAID, wherein the second portion of the in-use RAID isarranged according to a second array configuration having at least asecond parameter. The system also includes a first I/O component adaptedfor performing one or more first I/O operations according to the firstarray configuration, wherein the one or more first I/O operations areperformed on the data before the data is read by the data migratingcomponent and a second I/O component adapted for performing one or moresecond I/O operations according to a second array configuration, whereinthe second I/O operations are performed on the data after the data isread by the data migrating component, wherein a logical data structureof the in-use RAID is preserved.

In another general embodiment, a method includes reserving one or moreextents in a storage pool, reading data from a first portion of anin-use RAID, wherein the first portion of the in-use RAID is arrangedaccording to a first array configuration having at least a firstparameter, using the one or more reserved extents in the storage pool tostore at least a first portion of the data for writing to the in-useRAID, using one or more free extents in the storage pool or in thein-use RAID to store at least a second portion of the data for writingto the in-use RAID, writing the data to a second portion of the in-useRAID, wherein the second portion of the in-use RAID is arrangedaccording to a second array configuration having at least a secondparameter, performing one or more first I/O operations according to thefirst array configuration, wherein the one or more first I/O operationsare performed on the data before the data is read by the data migratingcomponent, and performing one or more second I/O operations according toa second array configuration, wherein the second I/O operations areperformed on the data after the data is read by the data migratingcomponent, wherein a logical data structure of the in-use RAID ispreserved.

In another general embodiment, a computer program product includes anon-transitory computer readable storage medium having computer readableprogram code embodied therewith, the computer readable program codeincluding computer readable program code configured to reserve one ormore extents in a storage pool, computer readable program codeconfigured to read data from a first portion of an in-use RAID, whereinthe first portion of the in-use RAID is arranged according to a firstarray configuration having at least a first parameter, computer readableprogram code configured to use the one or more reserved extents in thestorage pool to store at least a first portion of the data for writingto the in-use RAID, computer readable program code configured to use oneor more free extents in the storage pool or in the in-use RAID to storeat least a second portion of the data for writing to the in-use RAID,computer readable program code configured to write the data to a secondportion of the in-use RAID, wherein the second portion of the in-useRAID is arranged according to a second array configuration having atleast a second parameter, computer readable program code configured toperform one or more first I/O operations according to the first arrayconfiguration, wherein the one or more first I/O operations areperformed on the data before the data is read by the data migratingcomponent, and computer readable program code configured to perform oneor more second I/O operations according to a second array configuration,wherein the second I/O operations are performed, on the data after thedata is read by the data migrating component, wherein a logical datastructure of the in-use RAID is preserved.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as “logic”, a “circuit,” “module” or“system.” Furthermore, aspects of the present invention may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a non-transitory computer readable storage medium. Anon-transitory computer readable storage medium may be, for example, butnot limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium would include thefollowing: a portable computer diskette, a hard disk, a random accessmemory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), an optical storage device, a magnetic storagedevice, or any suitable combination of the foregoing. In the context ofthis document, a computer readable storage medium may be any tangiblemedium that can contain, or store a program for use by or in connectionwith an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwife, computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Morespecific examples (a non-exhaustive list) of the computer readablesignal medium would include the following: an electrical connectionhaving one or more wires, an optical fiber, etc. A computer readablesignal medium may be any computer readable medium that is not a computerreadable storage medium and that can communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

Generally speaking, preferred embodiments capable of RAID transformationin pooled storage as described herein include systems, methods, andcomputer program products incorporating features as follows.

In one embodiment, a system includes an extent reserving component whichis adapted for reserving one or more extents in a storage pool inoperation of a method and/or computer program product. Furthermore, thesystem includes a data migrating component which, in the course ofexecuting a method and/or computer program product, is adapted forreading data from a first portion of an in-use RAID arranged accordingto a first array configuration having at least a first parameter, usingreserved extents in the storage pool to store at least a first portionof the data for writing to the in-use RAID, using free extents in thestorage pool or in the in-use RAID to store at least a second portion ofthe data for writing to the in-use RAID, and writing the data to asecond portion of the in-use RAID. In these configurations, the secondportion of the in-use RAID is arranged according to a second arrayconfiguration having at least a second parameter.

Further still, the system includes a first I/O component adapted forperforming I/O operations on the data according to the first arrayconfiguration before the data is read by the data migrating componentand a second I/O component adapted for performing I/O operations on thedata according to a second array configuration after the data is read bythe data migrating component. Advantageously, systems including thesecomponents preserve the logical data structure of the in-use RAID duringoperation.

Alternative embodiments of the system as disclosed herein may includeadditional features and functionality, such as at least one parameter,including any or all of the following: a number of disks, a disk storagecapacity, an array storage capacity, a RAID level, etc., as would beunderstood by one having ordinary skill in the art upon reading thepresent descriptions.

Moreover, in preferred embodiments, any given array configuration may becharacterized by having a different number of disks, a different storagecapacity, and/or a different RAID level than that of otherconfigurations.

Referring specifically to the RAID, any RAID configuration as understoodby those having ordinary skill in the art as being capable oftransforming data from one portion of the RAID to another portion of theRAID while preserving the logical data structure of the data may beutilized. In one embodiment, such a RAID includes a first plurality ofdisks having a first capacity, and a second plurality of disks having asecond capacity, where a first array configuration uses the firstplurality of disks and the second plurality of disks, and a second arrayconfiguration uses either the first plurality of disks or the secondplurality of disks. Moreover, in some embodiments the first capacity maybe different than the second capacity.

The embodiments described above are made with primary reference to asystem having the specified fimctionality, but as would be understood bythose having ordinary skill in the art, the system may be used inconjunction with a process and/or computer program product designed tocarry out the operations described for each of the various systemcomponents. Moreover, the process and computer program product may beutilized with any system capable of transforming data in a RAID whilepreserving the logical structure of the data, as would be understood byone having ordinary skill in the art upon reading the presentdescriptions.

FIG. 1 illustrates a network architecture 100, in accordance with oneembodiment. As shown in FIG. 1, a plurality of remote networks 102 areprovided including a first remote network 104 and a second remotenetwork 106. A gateway 101 may be coupled between the remote networks102 and a proximate network 108. In the context of the present networkarchitecture 100, the networks 104, 106 may each take any formincluding, but not limited to a LAN, a WAN such as the Internet, PSTN,internal telephone network, etc.

In use, the gateway 101 serves as an entrance point from the remotenetworks 102 to the proximate network 108. As such, the gateway 101 mayfunction as a router, which is capable of directing a given packet ofdata that arrives at the gateway 101, and a switch, which furnishes theactual path in and out of the gateway 101 for a given packet.

Further included is at least one data server 114 coupled to theproximate network 108, and which is accessible from the remote networks102 via the gateway 101. It should be noted that the data server(s) 114may include any type of computing device/groupware. Coupled to each dataserver 114 is a plurality of user devices 116. Such user devices 116 mayinclude a desktop computer, lap-top computer, hand-held computer,printer or any other type of logic. It should be noted that a userdevice 111 may also be directly coupled to any of the networks, in oneembodiment.

A peripheral 120 or series of peripherals 120, e.g. facsimile machines,printers, networked and/or local storage units or systems, etc., may becoupled to one or more of the networks 104, 106, 108. It should be notedthat databases and/or additional components may be be utilized with, orintegrated into, any type of network element coupled to the networks104, 106, 108. In the context of the present description, a networkelement may refer to any component of a network.

According to some approaches, methods and systems described herein maybe implemented with and/or on virtual systems and/or systems whichemulate one or more other systems, such as a UNIX system which emulatesan IBM z/OS environment, a UNIX system which virtually hosts a MICROSOFTWINDOWS environment, a MICROSOFT WINDOWS system which emulates an IBMz/OS environment, etc. This virtualization and/or emulation may beenhanced through the use of VMWARE software, in some embodiments.

In more approaches, one or more networks 104, 106, 108, may represent acluster of systems commonly referred to as a “cloud.” In cloudcomputing, shared resources, such as processing power, peripherals,software, data, servers, etc., are provided to any system in the cloudin an on-demand relationship, thereby allowing access and distributionof services across many computing systems. Cloud computing typicallyinvolves an Internet connection between the systems operating in thecloud, but other techniques of connecting the systems may also be used.

FIG. 2 shows a representative hardware environment associated with auser device 116 and/or server 114 of FIG. 1, in accordance with oneembodiment. Such figure illustrates a typical hardware configuration ofa workstation having a central processing unit 210, such as amicroprocessor, and a number of other units interconnected via a systembus 212.

The workstation shown in FIG. 2 includes a Random Access Memory (RAM)214, Read Only Memory (ROM) 216, an I/O adapter 218 for connectingperipheral devices such as disk storage units 220 to the bus 212, a userinterface adapter 222 for connecting a keyboard 224, a mouse 226, aspeaker 228, a microphone 232, and/or other user interface devices suchas a touch screen and a digital camera (not shown) to the bus 212,communication adapter 234 for connecting the workstation to acommunication network 235 (e.g., a data processing network) and adisplay adapter 236 for connecting the bus 212 to a display device 238.

The workstation may have resident thereon an operating system such asthe Microsoft Windows® Operating System (OS), a MAC OS, a UNIX OS, etc.It will be appreciated that a preferred embodiment may also beimplemented on platforms and operating systems other than thosementioned. A preferred embodiment may be written using JAVA, XML, C,and/or C++ language, or other programming languages, along with anobject oriented programming methodology. Object oriented programming(OOP), winch has become increasingly used to develop complexapplications, may be used.

In conventional storage systems where data is stored on one or morearrays using RAID (hereinafter referred to as “RAID arrays”), parameterssuch as the number of disks in the RAID arrays, the size of the disks inthe RAID arrays and the RAID level used are fixed at array creation timein conventional methods. Once an array has been created and data hasbeen stored on it, it is typically impossible to change any of theseparameters without deleting the RAID array, destroying all the data, andre-creating the array with the new parameters.

In its broadest application, a preferred embodiment provides a system,method of operation, and computer program for controlling virtualizedvolumes stored on RAID arrays, adapted to migrate data from one part ofa RAID array to another without affecting the logical address that isused to address the data, and without requiring any RAiD-creation-timereservation of extents at each RAID array.

Moreover, preferred embodiments address the shortcomings of the state ofthe art by providing enhanced control of the location of the virtualizeddata, and the upfront reservation of spare capacity in accessiblestorage pools, thereby making it possible to transform the underlyingRAID array from one set of parameters to another, in place, withoutdestruction of data, and in a way that means the resulting data layoutis the same as, or close to the same as would be expected if a new RAIDarray was created with the new parameters.

Referring now to FIG. 3, a simplified schematic of a system 300 is shownaccording to one embodiment. Specifically, FIG. 3 shows a transformationsystem 300 for transforming an in-use RAID array 302 from a first arrayconfiguration 308 to a second array configuration 310, all whilepreserving a logical data structure (not shown) of the in-use RAID array302. The RAID array 302 comprises any number of independent disks 302A,302B, . . . , 302N, as would be appreciated by one of skill in the art.Additionally, the system 300 may comprise any number of other RAIDarrays (not shown). The system 300 also includes a pool extentreservation component 304 for reserving one or more reserved extents 307in a storage pool 301. The reserved extents may be reserved prior to thepool extent reservation component 304 reserving them (in which case theyare allocated for use with the RAID array 302) or it may reserve theextents for the first time.

According to preferred embodiments, the system 300 also includes a datamigrating component 306 for reading data from a first portion of thein-use RAID array 302 arranged according to the first arrayconfiguration 308, and writing the data to a second portion of thein-use RAID array 302 arranged according to the second arrayconfiguration 310 using one or more of the reserved extents 307 in thestorage pool 301 or one or more free extents 303 acquired at runtimefrom the storage pool 301 by a free extent locate and acquire component305.

In more embodiments, the system 300 further includes a first I/Ocomponent 312 adapted for performing I/O operations according to thefirst array configuration 308 on data prior to the data migrationcomponent 306 performing a read operation, and also a second I/Ocomponent 314 adapted for performing I/O operations according to thesecond array configuration 310 on data after the data migrationcomponent 306 writes the data.

Furthermore, the second array configuration 310 may include a greater orlesser number of disks than the first array configuration 308, e.g., adifferent number of disks, in one embodiment. In another embodiment, thesecond array configuration 301 may comprise a greater storage capacitythan the first array configuration 308, e.g., a different storagecapacity. Further still, in another embodiment, the disks in the secondarray configuration 310 may have a higher or lower RAID level than aRAID level of the first array configuration 308, e.g., a different RAIDlevel. Thus the system 300 may transform the RAID array 302 by changingthe array configuration parameters, for example, by changing the numberof disks in the array, the disk capacities, the RAID level, and/or otherparameters as would be understood by one having ordinary skill in theart upon reading the present descriptions.

As will be immediately clear to one of ordinary skill in the art, inpreferred embodiments, similar transformations may be performed for anyRAID arrays in the system 300 having access to storage pool 301.Moreover, the reserved extents 307 for storage pool 301 may be arrangedin any suitable manner across accessible storage, the RAID array 302,other RAID arrays, etc. Similarly, in preferred embodiments, the freeextent locate and acquire component 305 may be capable of locating andacquiring free extents 303 at runtime from any memory source, such asthe RAID array 302, other RAID arrays, memory in the storage pool 301,etc.

Referring now to FIG. 4, a method 400 for transforming a RAID array froma first configuration to a second configuration is shown according toone embodiment. The method 400 may be carried out in any desiredenvironment, including those described in FIGS. 1-3, according tovarious embodiments.

The method 400 starts at step 401, after which, extents in a storagepool are reserved at step 402. Preferably, extents are reserved when afirst RAID array is added to the storage pool, but may optionally alsobe performed at any time during the lifetime of the storage pool. When atransformation is requested, the migration process begins using anyavailable reserved extents at step 403. To ensure that the proper numberof extents are created, the method further includes determining whetheradditional extents are necessary for the migration process in step 404.

Furthermore, in some embodiments, whenever step 404 determines that moreextents are needed to perform the transformation, or that more extentsare required because the transformation has been started at the sametime as another transformation that is currently using the pool'sreserved extents, free extents in the storage pool are located andacquired for use in step 405.

Next, the migration of extents proceeds at step 406 by using thereserved and/or acquired extents to provide space for writing the data.After data is written to the reserved and/or acquired extents, theoriginal storage locations become available for further data migration.During the migration process, the I/O requests may continue to bereceived, as shown in step 407.

Subsequently, in step 408, it is determined if the I/O requests) refersto migrated or immigrated data. If the request refers to immigrated data(data which has not been written to the second portion of the RAID arrayyet), it is determined to use the first configuration, at step 409, toperform the I/O operation at step 411. Alternatively, if the requestrefers to migrated data (data which has already been written to thesecond portion of the RAID array), it is determined to use the secondconfiguration, at step 410, to perform the I/O operation at step 411.

Furthermore, the migration process continues at step 412, where it isdetermined whether the migration has completed. If it has not completed,the method 400 returns to step 406 and further extents are migrated. Theprocess completes when all of the required or requested migrations havebeen completed, as indicated at step 413.

In some embodiments, whenever an array transformation is initiated, thestorage system may instantiate two views of the drives comprising theRAID array. The first view utilizes the old configuration parameters,and the second view uses the new configuration parameters. Initially,all operations may be performed using the old view of the drives and soI/O would proceed normally, as described above.

Furthermore, during the transformation process, a first set of data maybe written from its original location on the RAID array to the reservedextents in the pool, according to one embodiment. When the reservedextents are filled, further extents may be acquired from among the freeextents in the pool. As will be clear to one of ordinary skill in theart, once data has been written from one or more original extents on theRAID array, those original extents are freed and may be used to writefurther data, thus freeing yet more extents until all the extents havebeen migrated.

As will be clear to one of skill in the art, preferred embodiments areparticularly useful in allowing the system, methods, and computerprogram products described herein to advantageously accept extensionsand modifications to the resources available in a RAID storage system,even after initiation of the RAID array.

As described, the preferred system dynamically uses free extents and asmall number of reserved extents from the storage pool to manage thetransformations instead of having statically reserved extents at the endof every RAID array, to great advantage over conventional approaches. Asa result, the effective capacity of each RAID array is not reduced.Instead, only very few extents required to support migrations andtransformations in the storage pool are excluded from use at any giventime.

In embodiments including a large configuration with many RAID arrays,mere is an additional advantage that significantly less space is held inreserve and thus unavailable to the user, ultimately allowing a greaterutilization of the user's storage. As more free extents exist in thestorage pool more transformations can be performed in parallel andtherefore more extents per RAID array can be transformed in parallel.

Thus, instead of reserving the extents at the end of every RAID array,the system may reserve a small number of extents once when the storagepool is created and make use of those and other See extents within thestorage pool to perform array transformations.

In a preferred embodiment, the system reserves, for example, fiveextents in the storage pool. These are hypothetical reservations, notreservations of any specific extents. Storage pool capacity reportsexclude these extents, and therefore the extents do not limit use of thestorage pool storage capacity. The system reserves the storage poolarray transformation extents when the first RAID array is added to astorage pool, in one approach, and frees the extents when the last arrayis removed from a storage pool, in another approach.

By reserving the small number of extents in the storage pool, thetransformation system is able to perform at least one arraytransformation at any time. As a result, the user is not burdened withensuring that there are free extents in the system. Furthermore, userscannot put themselves into a position where they desire to add capacityby adding drives to existing arrays but are unable to do so becausethere are not enough free extents in the pool to be able to start anarray transformation.

At the initiation of an array transformation, the transformation systemmay migrate extents from one end of the RAID array to the location ofreserved extents or other free extents in the storage pool. As a result,free extents may be created and reserved at the end of the array beingtransformed. The system then proceeds with the transformation usingthese free extents within the RAID array as if they were reservedextents.

Preferred array transformations can advantageously use the reservedextents as well as any other free extents in the storage pool to performarray transformations, and the use of the additional free extents isparticularly advantageous if more than one transformation is to beperformed simultaneously.

It will be clear to one of ordinary skill in the art that there is alimit to the availability of free extents, and thus, if moretransformations are invoked than there are free extents available tostart, the transformations for which extents cannot be found are queued,according to one embodiment. If the first array transformations addcapacity, when they complete, there will be additional free extentsremaining available in the storage pool and more array transformationscan subsequently be started utilizing those extents.

To enable accurate management and control of the storage pools, if thereare sufficient free extents such that multiple array transformations maybe performed at once, the storage pool capacities may be adjusted toexclude the extents already in use by the array transformation. Thesystem is also operable to reject an I/O request for deletion of a RAIDarray or other volume deletion from the storage pool if there are stillarrays in the storage pool and the deletions would eliminate the freespace represented by the extents reserved in the storage pool for arraytransformations, in one approach. Similarly, the system may reject RAIDarray transformations that reduce the capacity of a RAID array if suchtransformations would eliminate the free space represented by thereserved extents, in another approach.

In some embodiments of storage virtualization devices, the user may beable to configure a warning threshold on the storage pool to alert theuser if the storage pool's usage capacity is at a certain level withinthe total storage pool capacity. In such a system, the number of freeextents used for array transformation may be restricted to keep arraytransformation from temporarily causing the system to cross the warningthreshold.

It will be readily appreciated by one of ordinary skill in the art thatvarious further modifications to the embodiments described herein arepossible.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that, perform the specified functions or acts, or combinationsof special purpose hardware and computer instructions.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only; and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A system, comprising: a data migrating componentconfigured to: read data from a first portion of an in-use redundantarray of independent disks (RAID), wherein the first portion of thein-use RAID is arranged according to a first array configuration havingat least a first parameter; use one or more reserved extents in astorage pool to store at least a first portion of the data for writingto the in-use RAID; use one or more free extents in the storage pooland/or in the in-use RAID to store at least a second portion of the datafor writing to the in-use RAID; and write the data to a second portionof the in-use RAID, wherein the second portion of the in-use RAID isarranged according to a second array configuration having at least asecond parameter.
 2. The system as recited in claim 1, wherein the firstand second parameters comprise at least one of: a number of disks, adisk storage capacity, an array storage capacity, and a RAID level. 3.The system as recited in claim 1, wherein the second array configurationis characterized by having a different number of disks than the firstarray configuration.
 4. The system as recited in claim 1, wherein thesecond array configuration is characterized by having a differentstorage capacity than the first array configuration.
 5. The system asrecited in claim 1, wherein the second array configuration ischaracterized by having a different RAID level than a RAID level of thefirst array configuration.
 6. The system as recited in claim 1, whereinthe RAID comprises: a first plurality of disks having a first capacity;and a second plurality of disks having a second capacity, wherein thefirst array configuration uses the first plurality of disks and thesecond plurality of disks, and wherein the second array configurationuses either the first plurality of disks or the second plurality ofdisks, wherein the first capacity is different than the second capacity.7. The system as recited in claim 6, wherein the data migratingcomponent is further configured to determine that the one or more freeextents are needed for data migration based at least in part on whetherall reserved extents in the storage pool are currently being used. 8.The system as recited in claim 1, wherein the second array configurationis characterized by having a different number of disks than the firstarray configuration, wherein the second array configuration ischaracterized by having a different storage capacity than the firstarray configuration, wherein the second array configuration ischaracterized by having a different RAID level than a RAID level of thefirst array configuration, wherein the RAID comprises: a first pluralityof disks having a first capacity; and a second plurality of disks havinga second capacity, wherein the first array configuration uses the firstplurality of disks and the second plurality of disks, and wherein thesecond array configuration uses either the first plurality of disks orthe second plurality of disks.
 9. A method, comprising: reading datafrom a first portion of an in-use redundant array of independent disks(RAID), wherein the first portion of the in-use RAID is arrangedaccording to a first array configuration having at least a firstparameter; using one or more reserved extents in a storage pool to storeat least a first portion of the data for writing to the in-use RAID;using one or more free extents in the storage pool and/or in the in-useRAID to store at least a second portion of the data for writing to thein-use RAID; and writing the data to a second portion of the in-useRAID, wherein the second portion of the in-use RAID is arrangedaccording to a second array configuration having at least a secondparameter.
 10. The method as recited in claim 9, wherein the first andsecond parameters comprise at least one of: a number of disks, a diskstorage capacity, an array storage capacity, and a RAID level.
 11. Themethod as recited in claim 9, wherein the second array configuration ischaracterized by having at least one of: a different number of disksthan the first array configuration, a different storage capacity thanthe first array configuration, and a different RAID level than a RAIDlevel of the first array configuration.
 12. The method as recited inclaim 9, comprising determining that the one or more free extents areneeded for data migration based at least in part on whether all reservedextents in the storage pool are being used.
 13. The method as recited inclaim 9, comprising: receiving an I/O request, determining whether thereceived I/O request refers to unmigrated data or migrated data, theunmigrated data being the data from the first portion of the in-use RAIDthat has not been written to the second portion of the in-use RAID, themigrated data being the data from the first portion of the in-use RAIDthat has been written to the second portion of the in-use RAID,performing the I/O request according to the first array configurationupon determining that the I/O request refers to the unmigrated data; andperforming the I/O request according to the second array configurationupon determining that the I/O request refers to the migrated data. 14.The method as recited in claim 9, further comprising making the firstportion of the in-use RAID available for further data migration afterthe data is written to the one or more reserved extents and the one ormore free extents.
 15. A computer program product, the computer programproduct comprising a non-transitory computer readable storage mediumhaving computer readable program code embodied therewith, the computerreadable program code readable and/or executable by a processor to causethe processor to: read data from a first portion of an in-use redundantarray of independent disks (RAID), wherein the first portion of thein-use RAID is arranged according to a first array configuration havingat least a first parameter; use one or more reserved extents in astorage pool to store at least a first portion of the data for writingto the in-use RAID; use one and/or more free extents in the storage poolor in the in-use RAID to store at least a second portion of the data forwriting to the in-use RAID; and write the data to a second portion ofthe in-use RAID, wherein the second portion of the in-use RAID isarranged according to a second array configuration having at least asecond parameter that is different than the first parameter.
 16. Thecomputer program product as recited in claim 15, wherein the first andsecond parameters comprise at least one of: a number of disks, a diskstorage capacity, an array storage capacity, and a RAID level.
 17. Thecomputer program product as recited in claim 15, wherein the secondarray configuration is characterized by having a different number ofdisks than the first array configuration.
 18. The computer programproduct as recited in claim 15, wherein the second array configurationis characterized by having a different storage capacity than the firstarray configuration.
 19. The computer program product as recited inclaim 15, wherein the second array configuration is characterized byhaving a different RAID level than a RAID level of the first arrayconfiguration.
 20. The computer program product as recited in claim 15,wherein the second array configuration is characterized by having adifferent number of disks than the first array configuration, whereinthe second array configuration is characterized by having a differentstorage capacity than the first array configuration, wherein the secondarray configuration is characterized by having a different RAID levelthan a RAID level of the first array configuration.